ARC Joint: Anthropomorphic Rolling Contact Joint With Kinematically Variable Torsional Stiffness
Seungyeon Kim, Eunho Sung, Jaeheung Park
Abstract
As compliant joints not only compensate for the lack of actuated degrees of freedom of an under-actuated system and improve grasp stability but also prevent system failure from unexpected contacts, various types of compliant joints have been applied to end-effectors. Although joint compliance increases the success rate of power grasping, when the finger wraps around large objects, it can reduce the grasping success rate in pinch gripping when dealing with small objects using the fingertips. To overcome this drawback, we propose a novel rolling contact joint, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">anthropomorphic rolling contact joint</i> , that mimicked the structures of the human finger joint, tongue-and-groove, and collateral ligaments. The anthropomorphic rolling contact joint can passively adjust the torsional stiffness according to the joint angle without additional weight and space. With the anthropomorphic rolling contact joint, flexing the fingers for pinch grasping increases torsional stiffness of the joints and improves grasping stability. In this study, the characteristics and performance of anthropomorphic rolling contact joints were experimentally analyzed by varying the tongue-and-groove shape. Furthermore, it was demonstrated that the three-finger gripper with high torsional stiffness stably grasps small objects in the pinch grasping posture. In addition, because it is easy to manufacture, an anthropomorphic rolling contact joint has advantages in terms of maintenance.